Using Ionic Liquid in a Biphasic System to Improve Asymmetric Hydrolysis of Styrene Oxide Catalyzed by Cross-Linked Enzyme Aggregates (CLEAs) of Mung Bean Epoxide Hydrolases

Abstract

The asymmetric hydrolysis of racemic styrene oxide (SO) to (R)-1-phenyl-1,2-ethanediol using cross-linked enzyme aggregates (CLEAs) of epoxide hydrolases (EHs) from mung bean (mbEHs) was successfully conducted using ionic liquids (ILs) as cosolvents in biphasic systems. Of all the tested ILs, the best results were observed in the biphasic system containing [C4MIM][PF6] with better biocompatibility to the CLEAs of mbEHs. In the [C4MIM][PF6]/buffer biphasic system, it was found that the optimal volume ratio of IL to buffer, reaction temperature, buffer pH, and substrate concentration were 1:5, 40 °C, 7.5, and 120 mM, respectively. Under the optimized reaction conditions, the initial reaction rate, yield, product ee, and E value reached 3.35 mmol/min, 49%, 95.8%, and 151, respectively, which were much higher than the corresponding values reported previously. Furthermore, the CLEAs exhibited markedly enhanced operational stability in a [C4MIM][PF6]-based biphasic system as compared with an n-hexane-based biph...